People are generally aware of the most common causes of hallucinations, like schizophrenia and a really high fever. But lesser known are the more rare causes; here are six you probably haven't heard about.

Bullying is a national outrage, but when the victim is an autistic 16-year-old boy who was forced into sexual acts, beaten, and stabbed, the level of horror becomes intolerable. Seventeen-year-old Lauren Bush, who has just admitted to torturing the boy, committed the unthinkably cruel crime in March alongside a 15-year-old girl.

The Maryland teenage girls were originally charged with two counts of first-degree assault, two counts of second-degree assault, soliciting child pornography, and false imprisonment. Investigators discovered the girls made the autistic boy, who will remain unnamed because of his age, masturbate and have sex with a family pet. They recorded it on their cellphones and also held a knife to his throat, kicked his groin, dragged him around by his hair, and made him walk across a thinly frozen pond. When he fell through the ice twice, they did nothing to help him.

“His vulnerabilities made this crime more heinous,” St. Mary's Sheriff Tim Cameron told SoMdNews. Cameron added that the alleged offenses were one of the most disturbing crimes he had ever seen.

On May 29, Bush pled guilty before a St. Mary’s County judge to second-degree assault and distribution of an obscene video. She has since been sent to an out-of-state secure facility where she’ll remain until the court determines her release.

When the boy came home, his mother asked him why his clothes were wet and he told her he walked onto the pond on his own with no provocation from the girls. When the teens were arrested, Bush was going to be tried as an adult with several counts of assault, but after reevaluation, the courts decided a juvenile prosecution would be more appropriate given her age. The other girl is being charged as a juvenile, and her name is being withheld.

“He’s not a good judge of people,” the mother told The Washington Post in March. “I keep trying to talk to him about it, but it’s hard to get much out of him. I’ll say, ‘This is what so-and-so told me, and I know this happened,’ but he’ll act like, ‘Oh, [the girls] were just playing around.’ He didn’t deny anything. I am trying to make him understand that people are talking about this all over TV, but he wanted to go to school today.”

Since Bush was charged in a juvenile court, she will be released before she turns 21. That’s less than four years from the date of prosecution.

After the girls were arrested, the boy’s mother asked him: “You’re going to stay away from these girls, right? You don’t plan on hanging out with them again, right?” He answered, “I don’t know.”